1. Field of the Invention
This invention relates to text or word processing systems, i.e., information processing systems where the processing affects the format of the information. More particularly, it relates to a method for justifying a line of text containing complex characters formed from backspaces and overstrikes.
2. Description of the Prior Art
Word or text processing systems have been developed for formatting alphanumeric data into a suitable format for specified printed documents, e.g., letters, reports, text books, magazines and newspapers. In previous word processing systems, substantially all of the formatting was accomplished in the word processor. A word processor normally comprises a keyboard entry display terminal, storage means, and a central processor. The operator utilizing the display terminal arranges the information into a preselected alphanumeric line and page format. The system then transmits the alphanumeric data, together with the formatting data, to the printer for outputting the previously formatted document. More recent word or text processing systems have sought new approaches to increase the output of the system. Improved word processing systems have included formatting capability in the printer so that the word processor would be released to carry out further word or text processing activities as the foreground task, while the printer could function simultaneously to complete its formatting functions as a background task.
Formatters in printers associated with word or text processors basically convert an input data stream containing controls and EBCDIC characters into an output data stream containing escape, print, and index commands. The formatter performs its task by operating on the input data stream in two passes, the scan pass and format pass. In the scan pass, a line of text from the input data stream is preprocessed through the calculation and storage of certain parameter values for later use in the format pass. In the output pass, printer control commands are generated from the line of text for buffering and subsequent transmission to the printer control system.
One of the functions performed by the text formatter of a printer is justification, or the uniform expansion of interword spaces for the purpose of eliminating all or some other specified percentage of the blank space between the right-most graphic in a field and the right boundary of the field. The calculations necessary to perform the justification process are made during the scan pass and stored until the format pass where the space expansion process is performed. The basic functions performed during the justification process are as follows: determining the number of expandable spaces in a field, calculating the amount of blank space to be eliminated, determining which spaces are to be expanded, and adding an appropriate escapement value to the escapement of the expandable spaces.
The printer of a text or word processing system forms a complex character in two passes of the printhead. In the first pass, the line or a section of the line is printed, then the printer is backspaced and the complex character is formed by overstrikes, such as by underlining or accent marks added to the printed character. However, such complex characters formed in two passes of a printhead have presented a problem with respect to line justification. Since line justification involves varying the interword space, any conventional justification technique would present a problem involving an interword space which was backspaced across in order to form the complex character. The result of ordinary line justification would be an offset between the character printed in the first pass and the overstrike printed in the second pass. A need has thus arisen for a line justification technique for use in combination with the formation of complex characters formed from two passes of the printhead.